Tray loading apparatus for disc players

ABSTRACT

A control circuit of a tray loading apparatus determines, according to a disc size and a tray moving direction, a time during which to control the motor at a constant speed. When the specified time has elapsed after the motor was started, the control circuit produces a pulse-width modulated output to slowly lower the motor speed, eliminating impact noise when the tray strikes a stopper. This motor deceleration time is measured. When the measured deceleration time disagrees with a preset or previously detected target deceleration time, the difference is either added to or subtracted from a constant-speed motor operation time and the resultant value is taken as the next target time for constant-speed motor operation. In this way, by changing the time during which the motor is driven at a constant speed, any variations in the tray moving speed as might occur from varying loads on the motor are absorbed to keep the motor deceleration time and decelerating speed unchanged, thus making the tray motion smooth.

BACKGROUND OF THE INVENTION

The present invention relates to a tray loading apparatus in an opticaldisc player which moves the tray containing an optical disc (video disc,compact disc, etc.) to a position of a turntable for recording orreproducing the disc.

Prior Art

In such conventional tray loading apparatuses as mentioned above, thetray is drawn into or out of the disc player by meshing a motor-poweredgear with a rack formed on the tray and controlling the rotation of themotor.

The following methods are available for controlling the revolution ofthe motor.

(a) Switches are arranged one each at the finishing positions of thetray loading and unloading operations, and a certain voltage is appliedto the motor until one of the switches turns off, thus driving the trayat a specified constant speed.

(b) Switches are arranged one each at the finishing positions of thetray loading and unloading operations; another switch is located at anintermediate positions for the tray loading and unloading operations; acertain voltage is applied to the motor until one of the second switchesturns on and, after that second switch is turned on and until the switchat the finishing position turns off, the applied voltage to the motor isreduced to a specified level, thereby driving the tray at a constant lowspeed.

(c) Switches are provided one each at the finishing positions of thetray loading and unloading operations as with the method (a); a certainvoltage is applied to the motor for a specified length of time and,after the elapse of that period until one of the switches at thefinishing positions turns off, the applied voltage to the motor isslowly lowered by a pulse-width modulation so as to gradually reduce themoving speed of the tray.

The first motor control method (a) requires at least two switches,increasing the number of parts and making the apparatus costly. Anotherdrawback is that since the tray strikes with force the stoppers at thetray inserted and withdrawn positions, large impact noise is generated.

With the second method (b), because the tray moving speeds at theterminal or finishing positions of the loading and unloading operationsare slower, the impact noise is lower than that produced in the method(a). However, one additional switch is needed for speed reduction,increasing the parts count and therefore the manufacturing cost. Anotherdisadvantage is that the tray moving speed is abruptly changed,resulting in an unnatural behavior of the tray, which in turn mars animage as a quality product.

As to the third motor control method (c), although there is an advantageof lower impact noise because the tray moving speed at the stop positionis smaller than that in the method (b), this method has a drawback inthat as the mechanism load changes over a long period of use or due tomechanism parts variations from manufacturing errors, the traydecelerating speed will vary. As a result the tray speed at the finishposition cannot be the same at all times. Because of this, an attempt toperform a pulse-width modulation according to the mechanism loadrequires a very complicated circuit configuration.

SUMMARY OF THE INVENTION

It is an object of the invention to solve the aforementioned problemsand provide a tray loading apparatus for disc players in which, evenwhen a mechanism load changes over a long period of use or due tomechanism parts variations from manufacturing errors, the time in whichthe tray is driven in a decelerating state can be kept constant, makingit possible to perform the motor control in a predetermined constantdecelerating condition and thereby keeping the tray speed at the stopposition equal at all times.

To achieve the above objective, the tray loading apparatus for discplayers according to this invention comprises: a loading motorrevolution speed control means capable of performing a wide range ofmotor control from a constant speed control to a deceleration control; atimer for measuring a time which elapses from the start of motordeceleration to the end of deceleration; and a control circuit forcalculating a time during which the motor is to be driven at a constantspeed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the tray loading apparatus of the presentinvention;

FIG. 2 is a flowchart showing the sequence of operations according tothe present invention; and

FIG. 3 is a graph showing a behavioral characteristic of a moving tray.

PREFERRED EMBODIMENT OF THE INVENTION

One preferred embodiment of this invention will be described byreferring to the accompanying drawings. In FIG. 1, reference numeral Irepresents a motor for moving a tray between an inserted position and awithdrawn or ejected position. Denoted 2 is a motor drive circuit todrive and control the motor 1 through a pulse-width modulation.Designated 3, 4 are switches for detecting the tray located at finishingpositions of tray loading and unloading operations. A disc kindidentifying means 5 produces an output representing the size of a discplaced on the tray, a signal that indicates whether the disc is a videodisc, compact disc, or single disc (as described in Japanese PatentApplication No. Heisei 1-221706). A tray moving direction decision means6 produces an output indicating whether the tray should be moved in theinserting or withdrawing direction. Designated 7 and 8 are a timer and amemory, respectively. A control circuit 9 performs a series ofoperations as will be detailed in the flowchart of FIG. 2.

Now, referring to the flowchart of FIG. 2 and the operationcharacteristic diagram of FIG. 3, the operation of the apparatus withthe above configuration will be described.

First, when an eject or play operation is performed, the control circuit9 checks the output of the tray moving direction decision means 6 todecide in which direction--inserting or withdrawing direction--the trayis to be moved (step S1). The reason that the tray moving direction ischecked is that since the center of gravity of the tray differsdepending on the tray moving direction, the load acting on the motor 1.The loading time will vary according to the tray moving direction.

Following the check on the tray moving direction, the control circuit 9checks the output of the disc kind identifying means 5 to determine thesize of the disc (step S2). The reason for checking the disc size isthat because a different size of the disc has a different weight, achange will occur in the load acting on the motor 1. Therefore, in thetray loading time will change depending on the disc size.

The control circuit 9, taking into consideration the tray movingdirection and the disc kind, reads a preset time from memory 8 tocalculate a time t_(f) during which to control the motor 1 at a constantspeed (step S3). With the time t_(f) determined, the control circuit 9generates an output of a specified voltage for rotating the motor 1 atthe predetermined constant speed and sends it to a motor drive circuit 2(step S4). The motor 1 now starts rotating at the predetermined constantspeed, loading the tray at a constant speed.

Under this condition, the control circuit 9 monitors the time elapsed tocheck if the time t_(f) is exceeded (step S5). If the time has not beenreached, the processing returns to step S4; when the time is reached, atimer 7 is turned on (step S6). After this, the control circuit 9produces a pulse-width modulated output which will cause the motorrevolution speed to gradually slow down. The circuit 9 feeds this signalto the motor drive circuit 2 (step S7). As a result, the motor 1 slowlylowers its revolution while loading the tray at a decreasing speed.

During this loading operation, the control circuit 9 checks whether theterminal position detecting switch 3 or 4 is closed (step S8). When theswitch 3, 4 is not turned on, the processing returns to the step S7;when the control circuit 9 detects the closure of the switch 3, 4, itreads the time count of the timer 7 (step S9). Let us assume that thetime count at that moment is t_(p). The control circuit 9 then checks ifthe time t_(p) agrees with a preset or previously detected target value(step 10). When they match, the control circuit 9 ends the processingwithout rewriting the contents of the memory 8. When they do not agree,a check is made of whether the timer count is greater than the targetvalue (step S11).

When the timer count is greater than the target value, their differenceΔt is added to the time t_(f) and the resultant time is set as a newtarget time t_(f) in memory 8 (step S12). When the timer count issmaller than the target value, the difference Δt is subtracted from thetarget time t_(f) and the resultant time is set as a new target timet_(f) in memory 8 (step S13), which is used as the next target timet_(f) for loading operation. As a result, the time during which themotor 1 is gradually decelerated remains unchanged. Since a change inthe speed of the tray movement caused by the load variations istranslated into a change in the time in which the motor is driven at aconstant speed, the decelerating speed of the tray is not influenced bythe load variations but remains the same at all times.

As mentioned above, since the tray loading apparatus of this inventionabsorbs changes in the load applied to the motor by making variable thetime during which the tray is driven at a constant speed, thedecelerating speed at near the terminal position of the tray withdrawingand inserting operation can be kept at the same speed at all times. Notonly does this permit reliable withdrawal and insertion of the tray butalso eliminates impact noise produced when the tray strikes the stopper.The tray loading apparatus has another advantage of not requiring aswitch for speed change, contributing to a reduction in themanufacturing cost.

What is claimed is:
 1. A tray loading and unloading apparatuscomprising:driving means for driving a tray loading motor, which is usedto move a tray from an initial position to a terminal position, bycontrolling rotation speed of the motor; a timer for measuring time; anda control circuit for controlling said drive means and said timer,wherein said control circuit controls said drive means so that theloading motor is rotated at a constant speed for a set period of timeTF, and in response to an expiration of time period TF, said controlcircuit controls said drive means so that the rotation speed of theloading motor is gradually decreased in a deceleration period until thetray reaches a terminal position, said control circuit controlling saidtimer to measure a time duration of the deceleration period, saidcontrol circuit further calculating and updating the period of time TFbased on the time measured by said timer, for use during a subsequentloading or unloading process, during which said loading motor is to bedriven at a constant speed, in order to compensate for variations in aloading or unloading process, wherein the time period TF, for use duringthe subsequent loading or unloading process, is determined by adeviation between a target value and a value of time measured by saidtimer, said control means updating and setting said time period TF inaccordance with the deviation thus determined.
 2. A tray loading andunloading apparatus comprising:driving means for driving a tray loadingmotor, which is used to move a tray from an initial position to aterminal position, by controlling rotation speed of the motor; a timerfor measuring time; and a control circuit for controlling said drivemeans and said timer, wherein said control circuit controls said drivemeans so that the loading motor is rotated at a constant speed for a setperiod of time TF, and in response to an expiration of time period TF,said control circuit controls said drive means so that the rotationspeed of the loading motor is gradually decreased in a decelerationperiod until the tray reaches a terminal position, said control circuitcontrolling said timer to measure a time duration of the decelerationperiod, said control circuit further calculating and updating the periodof time TF based on the time measured by said timer, for use during asubsequent loading or unloading process, during which said loading motoris to be driven at a constant speed, in order to compensate forvariations in a loading or unloading process.
 3. The tray loading andunloading apparatus as recited in claim 2, wherein the time period TF,for use during the subsequent loading or unloading process, isdetermined by a deviation between a target value and a value of timemeasured by said timer, said control means updating and setting saidtime period TF in accordance with the deviation thus determined.
 4. Thetray loading and unloading apparatus recited in claim 3, furthercomprising:identifying means for identifying a type of recording mediumdisposed in the tray; and memory means for storing a plurality of timeperiods TF according to a plurality of recording medium types.
 5. Thetray loading and unloading apparatus recited in claim 4, wherein saidcontrol circuit monitors said timer and determines if a measured time ofthe deceleration period is greater than a target value, and in responseto such determination, said control circuit determines the deviationbetween the measured time and the target value, adds such deviation tothe time period TF stored in said memory means, and stores the resultantthereof.
 6. The tray loading and unloading apparatus recited in claim 4,wherein said control circuit monitors said timer and determines if ameasured time of the deceleration period is less than a target value,and in response to such determination, said control circuit determinesthe deviation between the target value and the measured value andsubtracts such deviation from the time period TF stored in said memorymeans, and stores the resultant thereof.
 7. The tray loading andunloading apparatus recited in claim 4, wherein the tray loads andunloads a compact disc into a compact disc apparatus.
 8. The trayloading and unloading apparatus recited in claim 2, wherein thevariations in the loading or unloading process are due to variations inthe load of the motor during the loading or unloading process.
 9. Thetray loading and unloading apparatus as recited in claim 2, furthercomprising identifying means for identifying a type of recording mediumdisposed in the tray, said control circuit setting the period of time TFaccording to the output of said identifying means.